WITH qq AS (SELECT

c.oid,

count(b.bufferid) * 8192 AS size,

(select sum(pages_mem) * 4096 from pgfincore(c.oid::regclass)) as size_in_pagecache

FROM pg_buffercache b

INNER JOIN pg_class c ON b.relfilenode = pg_relation_filenode(c.oid)

AND b.reldatabase IN (0, (SELECT oid FROM pg_database WHERE datname = current_database()))

GROUP BY 1)

pg_size_pretty(sum(qq.size)) AS shared_buffers_size,

pg_size_pretty(sum(qq.size_in_pagecache)) AS size_in_pagecache,

pg_size_pretty(pg_database_size(current_database())) as database_size

FROM qq;